#pragma once
#include <algorithm>
#include <cstdint>
#include <cstring>

// Based on https://github.com/vog/sha1
/*
Original authors:
Steve Reid (Original C Code)
Bruce Guenter (Small changes to fit into bglibs)
Volker Grabsch (Translation to simpler C++ Code)
Eugene Hopkinson (Safety improvements)
Vincent Falco (beast adaptation)
*/
namespace xfinal {
	namespace sha1 {

		static std::size_t constexpr BLOCK_INTS = 16;
		static std::size_t constexpr BLOCK_BYTES = 64;
		static std::size_t constexpr DIGEST_BYTES = 20;

		inline std::uint32_t rol(std::uint32_t value, std::size_t bits) {
			return (value << bits) | (value >> (32 - bits));
		}

		inline std::uint32_t blk(std::uint32_t block[BLOCK_INTS], std::size_t i) {
			return rol(
				block[(i + 13) & 15] ^ block[(i + 8) & 15] ^
				block[(i + 2) & 15] ^ block[i], 1);
		}

		inline void R0(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
			z += ((w&(x^y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
			w = rol(w, 30);
		}


		inline void R1(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
			block[i] = blk(block, i);
			z += ((w&(x^y)) ^ y) + block[i] + 0x5a827999 + rol(v, 5);
			w = rol(w, 30);
		}

		inline void R2(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
			block[i] = blk(block, i);
			z += (w^x^y) + block[i] + 0x6ed9eba1 + rol(v, 5);
			w = rol(w, 30);
		}

		inline void R3(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
			block[i] = blk(block, i);
			z += (((w | x)&y) | (w&x)) + block[i] + 0x8f1bbcdc + rol(v, 5);
			w = rol(w, 30);
		}

		inline void R4(std::uint32_t block[BLOCK_INTS], std::uint32_t v,
			std::uint32_t &w, std::uint32_t x, std::uint32_t y,
			std::uint32_t &z, std::size_t i) {
			block[i] = blk(block, i);
			z += (w^x^y) + block[i] + 0xca62c1d6 + rol(v, 5);
			w = rol(w, 30);
		}

		inline void make_block(std::uint8_t const* p, std::uint32_t block[BLOCK_INTS]) {
			for (std::size_t i = 0; i < BLOCK_INTS; i++)
				block[i] =
				(static_cast<std::uint32_t>(p[4 * i + 3])) |
				(static_cast<std::uint32_t>(p[4 * i + 2])) << 8 |
				(static_cast<std::uint32_t>(p[4 * i + 1])) << 16 |
				(static_cast<std::uint32_t>(p[4 * i + 0])) << 24;
		}

		template<class = void>
		void transform(std::uint32_t digest[], std::uint32_t block[BLOCK_INTS]) {
			std::uint32_t a = digest[0];
			std::uint32_t b = digest[1];
			std::uint32_t c = digest[2];
			std::uint32_t d = digest[3];
			std::uint32_t e = digest[4];

			R0(block, a, b, c, d, e, 0);
			R0(block, e, a, b, c, d, 1);
			R0(block, d, e, a, b, c, 2);
			R0(block, c, d, e, a, b, 3);
			R0(block, b, c, d, e, a, 4);
			R0(block, a, b, c, d, e, 5);
			R0(block, e, a, b, c, d, 6);
			R0(block, d, e, a, b, c, 7);
			R0(block, c, d, e, a, b, 8);
			R0(block, b, c, d, e, a, 9);
			R0(block, a, b, c, d, e, 10);
			R0(block, e, a, b, c, d, 11);
			R0(block, d, e, a, b, c, 12);
			R0(block, c, d, e, a, b, 13);
			R0(block, b, c, d, e, a, 14);
			R0(block, a, b, c, d, e, 15);
			R1(block, e, a, b, c, d, 0);
			R1(block, d, e, a, b, c, 1);
			R1(block, c, d, e, a, b, 2);
			R1(block, b, c, d, e, a, 3);
			R2(block, a, b, c, d, e, 4);
			R2(block, e, a, b, c, d, 5);
			R2(block, d, e, a, b, c, 6);
			R2(block, c, d, e, a, b, 7);
			R2(block, b, c, d, e, a, 8);
			R2(block, a, b, c, d, e, 9);
			R2(block, e, a, b, c, d, 10);
			R2(block, d, e, a, b, c, 11);
			R2(block, c, d, e, a, b, 12);
			R2(block, b, c, d, e, a, 13);
			R2(block, a, b, c, d, e, 14);
			R2(block, e, a, b, c, d, 15);
			R2(block, d, e, a, b, c, 0);
			R2(block, c, d, e, a, b, 1);
			R2(block, b, c, d, e, a, 2);
			R2(block, a, b, c, d, e, 3);
			R2(block, e, a, b, c, d, 4);
			R2(block, d, e, a, b, c, 5);
			R2(block, c, d, e, a, b, 6);
			R2(block, b, c, d, e, a, 7);
			R3(block, a, b, c, d, e, 8);
			R3(block, e, a, b, c, d, 9);
			R3(block, d, e, a, b, c, 10);
			R3(block, c, d, e, a, b, 11);
			R3(block, b, c, d, e, a, 12);
			R3(block, a, b, c, d, e, 13);
			R3(block, e, a, b, c, d, 14);
			R3(block, d, e, a, b, c, 15);
			R3(block, c, d, e, a, b, 0);
			R3(block, b, c, d, e, a, 1);
			R3(block, a, b, c, d, e, 2);
			R3(block, e, a, b, c, d, 3);
			R3(block, d, e, a, b, c, 4);
			R3(block, c, d, e, a, b, 5);
			R3(block, b, c, d, e, a, 6);
			R3(block, a, b, c, d, e, 7);
			R3(block, e, a, b, c, d, 8);
			R3(block, d, e, a, b, c, 9);
			R3(block, c, d, e, a, b, 10);
			R3(block, b, c, d, e, a, 11);
			R4(block, a, b, c, d, e, 12);
			R4(block, e, a, b, c, d, 13);
			R4(block, d, e, a, b, c, 14);
			R4(block, c, d, e, a, b, 15);
			R4(block, b, c, d, e, a, 0);
			R4(block, a, b, c, d, e, 1);
			R4(block, e, a, b, c, d, 2);
			R4(block, d, e, a, b, c, 3);
			R4(block, c, d, e, a, b, 4);
			R4(block, b, c, d, e, a, 5);
			R4(block, a, b, c, d, e, 6);
			R4(block, e, a, b, c, d, 7);
			R4(block, d, e, a, b, c, 8);
			R4(block, c, d, e, a, b, 9);
			R4(block, b, c, d, e, a, 10);
			R4(block, a, b, c, d, e, 11);
			R4(block, e, a, b, c, d, 12);
			R4(block, d, e, a, b, c, 13);
			R4(block, c, d, e, a, b, 14);
			R4(block, b, c, d, e, a, 15);

			digest[0] += a;
			digest[1] += b;
			digest[2] += c;
			digest[3] += d;
			digest[4] += e;
		}

	} // sha1

	struct sha1_context {
		static unsigned int constexpr block_size = sha1::BLOCK_BYTES;
		static unsigned int constexpr digest_size = 20;

		std::size_t buflen;
		std::size_t blocks;
		std::uint32_t digest[5];
		std::uint8_t buf[block_size];
	};

	template<class = void>
	inline void init(sha1_context& ctx) noexcept {
		ctx.buflen = 0;
		ctx.blocks = 0;
		ctx.digest[0] = 0x67452301;
		ctx.digest[1] = 0xefcdab89;
		ctx.digest[2] = 0x98badcfe;
		ctx.digest[3] = 0x10325476;
		ctx.digest[4] = 0xc3d2e1f0;
	}

	template<class = void>
	inline void update(sha1_context& ctx,
		void const* message, std::size_t size) noexcept {
		auto p = reinterpret_cast<
			std::uint8_t const*>(message);
		for (;;) {
			auto const n = (std::min)(
				size, sizeof(ctx.buf) - ctx.buflen);
			std::memcpy(ctx.buf + ctx.buflen, p, n);
			ctx.buflen += n;
			if (ctx.buflen != 64)
				return;
			p += n;
			size -= n;
			ctx.buflen = 0;
			std::uint32_t block[sha1::BLOCK_INTS];
			sha1::make_block(ctx.buf, block);
			sha1::transform(ctx.digest, block);
			++ctx.blocks;
		}
	}

	template<class = void>
	inline void finish(sha1_context& ctx, void* digest) noexcept {
		using sha1::BLOCK_INTS;
		using sha1::BLOCK_BYTES;

		std::uint64_t total_bits =
			(ctx.blocks * 64 + ctx.buflen) * 8;
		// pad
		ctx.buf[ctx.buflen++] = 0x80;
		auto const buflen = ctx.buflen;
		while (ctx.buflen < 64)
			ctx.buf[ctx.buflen++] = 0x00;
		std::uint32_t block[BLOCK_INTS];
		sha1::make_block(ctx.buf, block);
		if (buflen > BLOCK_BYTES - 8) {
			sha1::transform(ctx.digest, block);
			for (size_t i = 0; i < BLOCK_INTS - 2; i++)
				block[i] = 0;
		}

		/* Append total_bits, split this uint64_t into two uint32_t */
		block[BLOCK_INTS - 1] = total_bits & 0xffffffff;
		block[BLOCK_INTS - 2] = (total_bits >> 32);
		sha1::transform(ctx.digest, block);
		for (std::size_t i = 0; i < sha1::DIGEST_BYTES / 4; i++) {
			std::uint8_t* d =
				reinterpret_cast<std::uint8_t*>(digest) + 4 * i;
			d[3] = ctx.digest[i] & 0xff;
			d[2] = (ctx.digest[i] >> 8) & 0xff;
			d[1] = (ctx.digest[i] >> 16) & 0xff;
			d[0] = (ctx.digest[i] >> 24) & 0xff;
		}
	}
}